Remotely powered optical switch for remote subscriber aggregation and OTDR measurement in PON

Abstract

We present for the first time remote powering of a 3-D MEMS for optical switching using light over fibre. The low power switch with integrated optical splitters is suitable at non-powered remote PON distribution sites. Introduction The rapid deployment of fibre-to-the-home (FTTH) poses a number of new operational challenges in managing fibre due to the growing outside fibre plant infrastructure and the inherent churn in access networks [1]. Automating fibre management using remotely controlled optical switches has been proposed to efficiently manage subscriber connectivity and fault localization without human intervention, and to reduce the number of network and test equipment [2]. Early field trials have confirmed the benefits to operate and maintain fibrebased networks [3]. The deployment of switches in Central Offices (CO) for FTTH point-to-point networks is relatively simple. The insertion of optical switches, however, in Passive Optical Networks (PON) at Fibre Distribution Hub (FDH) sites in the field is much more difficult because those sites are usually not powered. We demonstrate in this paper a remotely powered fibre management solution using a low-power 3DMEMS optical switch and a light-over-fibre powering technique. We also report improved environmental performance for field switch operation. Integrated PON 3-D MEMS Switch Fig.1 shows a typical FDH layout in a PON: a first bay with optical splitters is connected to the Optical Line Terminal (OLT) at the CO; a second bay with fibre terminations is connected to residential homes. Optical splitters Patch-cords OLT ONU CO Homes Outside Plant Truck-rolls for patching Field OTDR measurements ONU FDH Fig. 1. PON FDH with discrete splitters and manual fibre management requiring technician dispatch to connect subscriber to OLT or test fibres with OTDR. Each time a subscriber is added, a technician must be dispatched at the FDH site to connect it to an unused OLT port. If subscribers are connected up-front, additional OLTs are required due to limited market penetration, thus increasing greatly the initial investment cost per paying subscribe. Technicians also go in the field to perform OTDR measurements to certify fibre installation or to trouble-shoot faults. All those costly and error-prone human interventions can be alleviated by the insertion of an optical switch at the FDH sites (Fig.2). The software-controlled switch connects a subscriber to the desired splitter port, packing subscribers onto the minimum number of OLTs in real time. All the home run fibres can be checked using a test fibre connected to an OTDR at the CO that can be shared among multiple FDH sites. Optical switch with splitters OLT ONU CO Outside Plant